Updated: July 15th, 2006
Well, the site is fast again (as fast as it can get on Dreamhost). As many Dreamhost users know, sites hosted with them are often slow to load with a high initial lag. I'm hosting 3 sites with them, and there are speed problems with all 3.
So after looking into it some more, I discovered that the problem is not the servers used (they are actually dual core 2+Ghz Opterons), and not the amount of RAM (4GB), or server load (usually 1-3, which for a dual core system shouldn't be bad at all). It is actually the nfs (network filesystem). All of Dreamhost files are sitting on nfs, which is mounted on the hosting servers. The problem with nfs, especially noticeable with a large amount of files, is that it's much slower than local disk access and is limited by network speed and congestion. Dreamhost is also looking into possible tweaks to nfs performance.
For comparison, I've installed Gallery2 (notorious for its size and slow speed) on Dreamhost and Bluehost. It's blazing fast on Bluehost, but is a couple of times slower on Dreamhost. I'm assuming that Bluehost is using a local filesystem because I don't see any other reason why it would be so much faster. So with that, I have disabled the Random Photo plugin for Lazyest-gallery which went through 2500+ files each time to figure out a random one to show (efficient approach, isn't it?). Until that is fixed, it's staying off this site.
In the meantime, if you found this article useful, feel free to buy me a cup of coffee below.